I want to add a switched circuit for accessories using a relay instead of wiring them directly to the ignition. Basically, the coil of the relay will be wired to the ignition (i think it's the blue wire but don't quote me), and switch battery current (via 6 or 8 gauge wire) to a small fuse panel. Is this the "right" way to do this? I always thought accessories in cars (such as the radio) ran off the main relay, but that isn't the case in the Trooper. I don't want to add a bunch of circuits to the ignition wiring without a relay. Right now, it will only be used for a heated o2 sensor and my 400w inverter (this also works through the cig lighter but gets hot above 150 watts load or so, hence the heavy wiring).

What's the best way to tap into the ignition wiring?

Are those insulation-displacement "vampire" taps (Scotchlocks) advised against?

I've done basically the same thing you're looking to do ...

My memory isn't 100% clear on the details, but I tapped the ACC circuit to drive the relay coil. Doing it this way, you also get the benefit of "load reduction" when you hit the starter; all accessories go OFF while starting.

If yer not in a rush to gitter done, gimmee a few days and I'll see if I can get some pics, and/or a schematic of what I did.

I wouldn't use the scotch-loks myself, I like a razor blade, solder, and heat shrink. But, I did notice that there are some "water-resistant" varieties out there now that probably would be OK for the low current stuff. I wouldn't try to draw any significant power through them.

Ah yes, you're right. I want "hot in run", not "hot in start and run". I'm pretty sure the radio is wired that way, and would be a convenient place to get power for the relay coil.



That would be helpful. Like I said I want to run the inverter off it, I need to check it again but at 400W full load I'm pretty sure it pulls close to 50A DC! (Can you say alternator upgrade?)



I prefer solder too, or a Weatherpack connector in lieu of splices. If I connect it to the radio, I can probably add a wire to the "power" pin on the connector - just piggyback it and solder in place. There's no need for weatherproofing in the cab (well, I suppose there could be...;) )

I dont like the scotch-loks either. They tend to cut strands of the wire if not done just right and can creat a 'hot spot' in the wire. I basicly do the same thing as TS, cut the wire I want to tap into, strip the ends, then solder the wires together and heat shrink it.

Every wire on my tail lights are soldered and heat shrinked now because previous owners tapped into them for trailer wiring. I cut all that out and got the plug in kit.

Radio Shack butane soldering irons are very handy when doing wiring work on cars.



It shouldnt be that high. My 750w inverter is internally fused for 30 amps and I havent blown one yet. I still need to mount mine. I'm thinking of putting it in the tail gate where the net bin is. Everything I put in there falls out so no big deal losing the storage, I dont use it. Just not sure about running the power cables into the tailgate.

That's what the inverter is for! I wonder if "Cold Heat" is junk or not? $16 at Harbor Freight... I've never tried a butane one, maybe I'll splurge.

So I should redo my trailer wiring then? <img src="/forums/images/graemlins/wink.gif" alt="" /> No plug-in kit available for 1st Gens AFAIK. Like I said I like to use weatherpacks for splices, but for 3-way splices that won't work. I don't like crimp stuff (I crimp the Weatherpacks but add a bit of solder), I never feel like it's 100% right. The only problem with solder is that it doesn't flex. But if the new circuit is soldered to a wire inside a connector that should provide mechanical support... thanks for your replies.

I got one and its only good for very light circuitry soldering. 18-24 gage wire. Needless to say I was dissappointed.

OK, as promised, here are some details on how I added the accesory relay on my 88 .

I wanted to use as much existing wiring as possible, so I combed the schematics carefully.

I found a connector behind the pass headlamp that was always hot, fed with a fairly heavy wire, right off the fusible links. The schematic called this a plug for optional headlamp washer/wiper.

To tap the ACC circuit in the fuse box, I found that there was already a wire in the harness from the fuse box over to underneath the relay bracket on the pass side. I don't have power windows, so I was free to use this wire, eliminating the need to run a wire across. If you do have power windows on yer rig, you can tap the ACC circuit the same way, but instead of using the existing wire, just run the wire from the new fuse out through one of the empty fuse holders and across to where ever you mount your relay.

Using various combinations of male and female fast-on connectors, I was able to connect to the various parts of the wiring harness without cutting or splicing anything! The beauty of this installation is that if I decide to revert to stock, I just unplug everything and pull it all out.

Inside fusebox:



Close-up of added fuse adapter:



This is where I tapped the 12V Hot from:



Wire plugged into that connector. This 12ga runs up to the relay under the bracket.



Another view, showing the 20A fuse. If you need more current than this, tap directly to the battery with a heavier wire:



Relays mounted in empty spaces under this bracket:



Ran the wiring:



If you are using the power window circuit for the coil of the accesory relay, you will find the connector taped to the harness under the relay bracket. Use a male fast-on pushed into that connector, and wire to one side of the coil. Other side of the coil goes to ground, which can be picked up where ever convenient. I used a ground in one of the connectors with another male fast-on.

The hot wire FROM the added relay, along with a 12ga ground that I picked up from the battery tray negative connection run through the grommet to a fuse panel (not pictured) that I built and installed under the dash in a tupperware container. It's tucked up under the dash and zip-tied in place so that when I need to add/remove accesories, I just cut the ties, and it's right there in easy reach to make connections to.

I don't think you'll need a schematic, but if anything is unclear, just let me know and I'll try to elaborate.

Excellent post, Jeff! <img src="/forums/images/graemlins/kewl.gif" alt="" />

Thanks for taking the time and effort and sharing your car hacks. <img src="/forums/images/graemlins/smile.gif" alt="" /> (And, I don't mean hack job, but hacking in the most complementary way.) Your explanations are clear, and are conveyed easily with your captioned images. Enjoy your New Year!

Jim <img src="/forums/images/graemlins/patriot.gif" alt="" />

I am going to lock this thread, but not for the usual reasons.

This is an outstanding thread that needs to be moved to the Archives. However, but locking it now but leaving it here for a few days, people will have a chance to view it, but we won't collect superfluous comments that would have to be edited out before the thread is moved to the archives.

If anyone has questions about the process, please open a new thread.

Again, a great thread <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />